Large workpieces, such as for example escalator steps or moving walkway plates, can be provided with a color coating, wherein the color coating is applied by means of, for example, a powder coating process. The workpieces are in such a case pretreated, powder coated, and subsequently post-treated. The pretreatment may comprise, for example, degreasing and washing, followed by anodizing and then, for example, washing and drying. The post-treatment may comprise, for example, stoving or baking of the coloration powder applied to the workpiece. Apart from the anodizing, the workpieces are treated in a continuous running process, wherein the workpieces continuously run or pass through a treatment unit and remain in the treatment unit for a predetermined transit time. Large currents are necessary for the anodizing of large workpieces with correspondingly large surfaces, such as for example escalator steps or moving walkway plates provided with ribs, and the loading of the anodizing tank has to be undertaken in individual batches. The workpieces are moved from the conveying means of the preceding treatment unit, wherein several workpieces are arranged in suitable basket-like trusses or on common carriers, are immersed in the tank and are connected to current cables. After the current treatment the trusses or carriers are lifted out of the task and transferred to the conveying means of the succeeding treatment unit.
A disadvantage of the known powder coating process is the batch-by-batch production sequence for the anodizing. The loading and unloading of the anodizing tank in batches limits the production output of the entire powder-coating plant.
The present invention avoids the disadvantages of the known equipment and provides equipment for surface treatment, by means of which a noticeable increase in productivity in achievable.
The advantages achieved by the invention are essentially to be seen in that all treatment steps can be carried out in continuous running operation, wherein merely a single continuously moving conveying means is needed for conveying the workpieces. The continuous running treatment improves the quality of the workpiece surface and increases the output of the plant as well as, in addition, being less personnel intensive.
In accordance with the invention, equipment for treatment of workpieces consists of at least one unit for treating the surface of the workpieces. In at least one of the units the workpieces are treatable by high currents its the workpieces continuously run through the equipment. A current feed is provided for the workpieces, to which carriers which transport the workpieces are connected. The carriers travel along a track which may allow the workpieces to pass continuously through pre-treatment, high-current treatment, and post-treatment stages.
The carrier may comprise a retaining device for the workpiece and means for passing the current into the workpiece. In a preferred embodiment the retaining device may take the form of a fork-shaped bracket with first and second limbs each with first and second retaining claws to hold the workpiece. The retaining claws may be provided with contact surfaces for current introduction into the workpiece.